The use of radiation to treat medical conditions comprises a known area of prior art endeavor. For example, radiation therapy comprises an important component of many treatment plans for reducing or eliminating unwanted tumors. Unfortunately, applied radiation does not discriminate between unwanted structures and adjacent tissues, organs, or the like that are desired or even critical to continued survival of the patient. As a result, radiation is ordinarily applied in a carefully administered manner to at least attempt to restrict the radiation to a given target volume.
Many treatment plans provide for exposing the target volume to radiation from a number of different directions. Arc therapy, for example, comprises one such approach. In such a case it often becomes useful or necessary to adjust the radiation-treatment platform to accommodate various differences that occur or accrue in different fields when moving the radiation source with respect to the target volume. A radiation-treatment plan therefore often provides information regarding useful or necessary adjustments to the radiation-treatment platform during such a treatment.
For ease of planning and implementation, in many cases the radiation beam is flattened using one or more flattening filters. Notwithstanding this flattening, a typical treatment plan endeavors to ensure that the isocenter of each administered beam is the same (and typically in the center of the beam) regardless of the administration angle and other field considerations. Unfortunately, this often leads to higher intensity in the middle of the planned treatment volume and a resultant wasting of energy in order to assure the right overall dose distribution.
Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. Certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. The terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.